Embedding Quicksight GenerativeQnA for Registered Users "QuickSightEmbedding is not defined"

I am trying embed Quicksight GenerativeQnA but facing difficulty.

I have created a server in flask/python which is running and getting embed_url and sanitizing it. On frontend I have created a script which gets data.

<script>
        async function embedQuickSightSearch() {
            const response = await fetch('http://localhost:4200/get-embed-url?user_name=bhavinb');
            const data = await response.json();

            document.getElementById('debugInfo').innerText = `Received URL: ${JSON.stringify(data)}`;
            if (data.error) {
                document.getElementById('errorMessage').innerText = `Error: ${data.error}`;
                return;
            }

            const { embedUrl } = data;

            const options = {
                url: embedUrl,
                container: document.getElementById('embeddingContainer'),
                height: "600px",
                width: "800px",
                onChange: (event) => {
                    console.log('QuickSight Q Event:', event);
                }
            };

            try {
                const result = await QuickSightEmbedding.embedSearchEmbed(options);
                console.log('QuickSight Q Embed Success:', result);
            } catch (error) {
                console.error('QuickSight Q Embed Error:', error);
                document.getElementById('errorMessage').innerText = `Embedding Error Here: ${error.message}`;
            }
        }
        embedQuickSightSearch();
    </script>

But I am getting "Embedding Error Here: QuickSightEmbedding is not defined".

Note : I have added the domin(http://localhost:4200/) on Quicksight's Manage Domain section. Proper validations of credentials are passed, as a result I am getting embed_url.

Any advice would be helpful.